This invention relates to a spectrometer apparatus and more particularly to a spectrometer apparatus which includes a holographic grating and a step order sorting filter.
Prior to the present invention, spectrometers useful in spectrum and spectrochemical analysis have been available. The prisms or flat gratings which have been utilized in spectrometers largely have been replaced with concave holographic gratings which permit collimating and refocusing a light beam at the same time while eliminating aberration in the focus. A concave holographic grating is a grating formed on a concave mirror that contains a large number of closely spaced grooves formed by exposing a photoresist with light from a laser source.
Depending upon the ratio of incident light wavelength to groove spacing, there may be one or a large number of directions in which a light from each groove interferes constructively with that of the other grooves. The number of such directions comprises the number of grating orders. In order to sample more than one order of the grating, it is necessary to scan the spectrometer by moving the grating or detector in the spectrometer or to take a multiplicity of exposures using a standard order sorting filter.
Accordingly, it would be desirable to provide a spectrometer which permits monitoring a plurality of grating orders simultaneously without the need for mechanical scanning.